The research reported in this dissertation focuses on the response of grain boundaries in polycrystalline metallic nanostructures to applied strain using molecular dynamics simulations and empirical interatomic force laws. The specific goals of the work include establishing how local grain boundary structure affects deformation behavior through the quantitative estimation of various plasticity mechanisms, such as dislocation emission and grain boundary sliding. The effects of strain rate and temperature on the plastic deformation process were also investigated. To achieve this, molecular dynamics simulations were performed on both thin-film and quasi-2D virtual samples constructed using a Voronoi tessellation technique. The samples were subjected to virtual mechanical testing using uniaxial strain at strain rates ranging from 105s-1 to 109s-1. Seven different interatomic embedded atom method potentials were used in this work. The model potentials describe different metals with fcc or bcc crystal structures. The model was validated against experimental results from studying the tensile deformation of irradiated austenitic stainless steels performed by collaborators at the University of Michigan. The results from the model validation include a novel technique for detecting strain localization through adherence of gold nanoparticles to the surface of an experimental sample prior to deformation. Similar trends with respect to intergranular crack initiation were observed between the model and the experiments. Simulations of deformation in the virtual samples revealed for the first time that equilibrium grain boundary structures can be non-planar for model potentials representing fcc materials with low stacking fault energy. Non-planar grain boundary features promote dislocation as deformation mechanisms, and hinder grain boundary sliding. This dissertation also reports the effects of temperature and strain rate on deformation behavior and correlates specific deformation mechanisms that originate from grain boundaries with controlling material properties, deformation temperature and strain rate. / Ph. D.

Structural Health Monitoring (SHM) of automobile tires has been an active area of research in the last few years. Within this area, the monitoring of strain on tires using wireless devices and networks is gaining prominence because these techniques do not require any wired connections. Various tire manufacturers are looking into SHM of automobile tires due to the Transportation Recall Enhancement, Accountability and Documentation (TREAD) act which demands installation of tire pressure monitoring devices within the tire. Besides measuring tire pressures, tire manufactures are also examining ways to measure strain and temperature as well to enhance overall safety of an automobile. A sensor system that can measure the overall strain of a tire is known as a centralized strain sensing system. However, a centralized strain sensing system cannot find the location and severity of the damage on the tire, which is a basic requirement. Various sensors such as acceleration and optical sensors have also been proposed to be used together to get more local damage information on the tire. In this thesis we have developed a strain sensing system that performs local strain measurements on the tire and transmits them to a console inside the vehicle wirelessly. Our sensing system utilizes a new sensing material called Metal RubberTM which is shown to be conductive like metal, and flexible as rubber. Also, we have also developed a reliable and an energy efficient geographic routing protocol for transporting strain data wirelessly from a tire surface to the driver of the automobile. / Master of Science

Syftet med denna fallstudie har varit att, med hänsyn till rådande försämrat säkerhetsläge, granska hur anställda inom försvarsindustrin beskriver företags brottsutsatthet. Vidare har syftet varit att diskutera hur brottsutsattheten kan förklaras utifrån kriminologisk teori. Detta har gjorts med semistrukturerade intervjuer, där anställda inom försvarsindustrin varit intervjudeltagare. Intervjudatan relaterades sedan till rutinaktivitetsteorin samt strainteorin. Av studiens huvudresultat har det framgått att anställda på företag i försvarsindustrin upplevde att företagens brottsutsatthet i huvudsak bestod av verkstadsstölder, cyberbrott, IP-intrång samt otillåten informationsspridning. Denna brottsutsatthet kunde förklaras av rutinaktivitetsteorin i vissa fall, samt i kombination med strain i andra fall. Brottsutsattheten upplevdes ha ökat i samband med att landets säkerhetsläge försämrades samt det huvudsakliga företaget expanderade personellt. Studiens viktigaste slutsatser var att brottsutsattheten i stort upplevdes ha ökat gällande samtliga ovan nämnda brott, men att orsaken till ökningen skiljde sig åt och att endast för cyberbrott upplevdes det föreligga ett samband med säkerhetsläget. / This case study examined how defense industry employees perceive crimes against their companies, in the context of a deteriorating security situation. Semi-structured interviews were conducted with employees, and the data was analyzed in relation to routine activity theory and strain theory. The main findings show that employees perceived the companies' exposure to crime mainly as a result of workshop thefts, cybercrime, IP infringement, and unauthorized dissemination of information. This crime exposure can be explained by routine activity theory in some cases and strain theory in others. The crime exposure increased as the country's security situation deteriorated and the main company expanded its personnel. The most important conclusions of the study were that crime exposure was generally perceived to have increased for all the above-mentioned crimes, but that the reason for the increase differed and that only for cybercrime was there perceived to be a connection with the security situation.

The Thesis deals with Strain-Space Plasticity and its implementation in Nonlinear Finite Element frame-work coupled with damage. Conventional Stress-Space Plasticity, though very popular amongst commercial nonlinear FEM software package, has severe limitations especially in dealing with perfect-plasticity situations and also for softening behaviour. Strain-Space Plasticity, when fully evolved, has the potential to replace the Stress-space Plasticity. The thesis is a welcome addition in furthering the understanding of Strain-Space Plasticity and its illustration to analyze practical engineering problems. Continuum Damage Mechanics (CDM) is an evolving area of Solid Mechanics with great potential for application in failure and integrity analyses. Research activities have been initiated by several research groups world-wide, thus demonstrating its acceptance as an area of mechanics in its own right .This thesis further demonstrates coupling of Continuum Damage Mechanics with Strain-Space Plasticity. The thesis has been organized into 11 chapters with a good review of Plasticity (Stress-Space as well as Strain-Space), CDM, Stainless-steel Plasticity as well as Adhesive Plasticity. Main research contributions include: Formulation, FEM implementation and benchmarking of Strain Space Plasticity for Plane-Stress, Plane Strain, Axi-symmetric as well as 3-D case. Both isotropic and kinematic hardening models have been implemented. Further, these implementations have been extended by coupling with Damage. Special illustrations have been made to practical situations involving constitutive modeling of Stainless-steel and structural-adhesive.

In der Arbeit wird gezeigt, wie man die Bodensteifigkeit bei sehr kleinen Dehnungen sowie die Abnahme der Steifigkeit mit zunehmender Scherdehnung in Labor- und Feldversuchen ermitteln kann. Dazu werden typische Eigenschaften mineralischer und organischer Böden einschließlich Korrelationen zusammengestellt und wesentliche Unterschiede zum Bodenverhalten bei großen Dehnungen, insbesondere hinsichtlich der Steifigkeit und der Spannungsabhängigkeit aufgezeigt. Weiterhin wird dargelegt, wie man mit dem hypoplastischen Stoffgesetz mit intergranularen Dehnungen das Bodenverhalten bei kleinen Dehnungen wirklichkeitsnah erfassen kann und wie die Stoffparameter zu bestimmen sind. Für die realistische Erfassung des Bodenverhaltens infolge zyklischer Belastung einschließlich der Ausbildung von Hystereseschleifen wird eine Modifizierung des hypoplastischen Stoffgesetzes unter Einführung eines zusätzlichen Stoffparameters vorgenommen. Es wird gezeigt, wie dieser Parameter in zyklischen Laborversuchen bestimmt werden kann und wie damit die Akkumulation von Dehnungen bei drainierten Bedingungen bzw. von Porenwasserdrücken bei undrainierten Bedingungen zuverlässig prognostiziert werden kann. Anhand der dynamischen Beanspruchung eines Eisenbahndammes auf weichem, organischem Untergrund wird das modifizierte hypoplastische Stoffgesetz mit intergranularen Dehnungen für ein bodendynamisches Randwertproblem angewendet und gezeigt, dass damit das Bodenverhalten realistisch abgebildet werden kann. Die Berechnungsergebnisse zeigen eine gute Übereinstimmung mit Ergebnissen von Schwingungsmessungen und Langzeitverformungsmessungen. Es werden bodendynamische Berechnungen zur Wellenausbreitung sowohl eindimensional als auch im Halbraum mit unterschiedlichen Stoffgesetzen geführt und Vergleiche mit analytischen Lösungen vorgenommen. Dazu wird gezeigt, welche Anforderungen an numerische Berechnungen zur Wellenausbreitung, insbesondere hinsichtlich Wahl der Zeitschritte, Elementgröße bzw. Knotenabstände, Größe des FE-Netzes und Modellierung der FE-Ränder erforderlich sind. / In this thesis it is shown how to determine the soil stiffness at very small strains, as well as the decrease in stiffness with increasing shear strain amplitude in laboratory and field tests. Typical properties and empirical correlations of coarse-, fine-grained and organic soils are collected and significant differences in soil stiffness and stress-dependence at small strains compared to large strains are shown. Further it is shown how one can realistically reproduce the soil behaviour at small strains with the hypoplastic constitutive model with intergranular strains and how the material parameters are determined. For a realistic prediction of soil behaviour due to cyclic loading including hysteresis loops in the stress-strain relationship, a modification of the hypoplastic constitutive model is made by using an additional material parameter. It is shown how this additional parameter can be determined in cyclic laboratory tests and how the accumulation of strains in drained conditions and excess pore pressures built up in undrained conditions can be realistically reproduced. Based on the dynamic load on a railway embankment on soft marshy ground, the modified hypoplastic constitutive model with intergranular strains is applied for a boundary value problem. It is demonstrated, that the soil behaviour can be reproduced realistically. Numerical results show a good agreement with results of vibration measurements and measurements of permanent displacements. A dynamical numerical analysis is performed for both one-dimensional and half-space conditions. Different constitutive models have been applied and compared with analytical solutions. The results demonstrate requirements on numerical analysis of wave propagation, in particular with regards to time steps, element size, node spacing, size of the FE mesh and boundary conditions.

Mg-Druckgusslegierungen sind aufgrund ihrer geringen Dichte potenzielle Leichtbauwerkstoffe. Ihre Festigkeitseigenschaften werden durch erhöhte Temperatur und die druckgussprozessbedingte Porosität maßgeblich beeinflusst. Zur Auslegung zyklisch belasteter Mg-Druckgussbauteile für eine begrenzte Betriebsdauer kann das Örtliche Konzept verwendet werden. Im Örtlichen Konzept nimmt das zyklische Werkstoffverhalten eine zentrale Rolle ein. Es umfasst das zyklische Verformungsverhalten und das zyklische Ermüdungsverhalten. Zur Beschreibung des zyklischen Werkstoffverhaltens werden die zyklische Spannungs-Dehnungs-Kurve für das Verformungsverhalten und die Dehnungswöhlerlinie für das Ermüdungsverhalten verwendet. Ziel der vorliegenden Arbeit ist es, die Einflüsse Temperatur und Porosität auf das zyklische Werkstoffverhalten der Mg-Druckgusslegierungen AZ91 und AM50 quantitativ zu erfassen. Dazu wird ein objektives Regressionsverfahren ermittelt, mit dem die zyklische Spannungs-Dehnungs-Kurve und die Dehnungs-Wöhler-Linie gemeinsam unter Einhaltung der Kompatibilitätsbedingungen aus den Daten einer Versuchsreihe regressiert werden können. Desweiteren wird eine Methodik entwickelt, mit der Ansätze zur quantitativen Erfassung von Einflüssen auf das zyklische Werkstoffverhalten aus Versuchsdaten abgeleitet werden können. Diese Methodik wird zur Untersuchung der Einflüsse Temperatur und Porosität auf das zyklische Werkstoffverhalten der Mg-Druckgusslegierungen AZ91 und AM50 angewendet. Die Untersuchungsergebnisse und deren Validierungen werden in dieser Arbeit vorgestellt. / Die-cast magnesium alloys are potential light-weight materials due to their low density. Their mechanical properties are significantly affected by elevated temperatures and by porosity, which die castings are especially prone to. The local strain approach can be used for dimensioning cyclically loaded magnesium die castings for a limited service life. The central role of this approach is assigned to the cyclic material behaviour. The cyclic material behaviour includes the cyclic deformation behaviour and the cyclic fatigue behaviour. It is characterized by the stress-strain curve for the cyclic deformation behaviour and by the strain-life curve for the cyclic fatigue behaviour. In the present work the aim is to describe the influence of elevated temperatures and of porosity on the cyclic material behaviour quantitatively. Therefore, a method is developed, which allows an objective and combined regression of the stress-strain curve and the strain-life curve for one test series. Furthermore, a methodology is developed, for deriving a formulation from experimental data to describe an arbitrary influence on the cyclic material behaviour quantitatively. This methodology is used to study the influences of elevated temperature and of porosity on the cyclic material behaviour of the die-cast magnesium alloys AZ91 and AM50. The results of the investigations and their validation are presented in this treatise.

O presente estudo avalia a associação entre estresse no trabalho e auto-relato de diagnóstico médico de lesão por esforço repetitivo (LER). Trata-se de um estudo seccional, inserido no Estudo Pró-Saúde, que consiste no acompanhamento de uma coorte de funcionários técnico-administrativos de uma universidade no Estado do Rio de Janeiro. Os dados foram obtidos, no ano de 2001, a partir da aplicação de um questionário auto-preenchível. A população de estudo constou de 3.314 funcionários, dentre os quais, 485 apresentaram auto-relato de diagnóstico médico de LER, após sua admissão como funcionários da universidade. A prevalência de LER foi maior entre as mulheres (19,4%) do que entre os homens (8,8%). O estresse no trabalho foi avaliado através da versão reduzida do Job Content Questionnaire, desenvolvido por Karasek e Theorell, cujas questões se destinam a avaliar a demanda psicológica, o controle sobre o próprio trabalho e, o apoio social no trabalho. A análise do estresse no trabalho foi realizada de acordo com os quadrantes propostos por Karasek (1979): baixa exigência (baixa demanda e alto controle); trabalho passivo (baixa demanda e baixo controle); alta exigência (alta demanda e baixo controle) e; trabalho ativo (alta demanda e alto controle). Nesta análise, utilizou-se como categoria de referência, a baixa exigência, por compor um cenário ideal de trabalho. Após ajuste por variáveis socioeconômicas e demográficas (idade, escolaridade e renda familiar per capita) e, ocupacionais (anos de trabalho na universidade e ocupação), homens e mulheres com alta exigência no trabalho, apresentaram uma chance maior de serem acometidos por LER (homens: OR= 1,88; IC95% 1,07-3,29 e mulheres: OR= 1,90; IC95% 1,32-2,02). No ajuste adicional pelo apoio social no trabalho, houve redução da força da associação, para ambos os sexos. Para as mulheres com alta exigência no trabalho, esta associação manteve-se significativa (OR= 1,63; IC95%= 1,12-2,37); enquanto que para os homens, esta associação ficou marginalmente significante (OR= 1,62; IC95%= 0,91-2,87). Este estudo reforça que o desequilíbrio entre a demanda psicológica no trabalho e o controle sobre o próprio trabalho é importante na ocorrência de LER e, portanto, pode ser útil na elaboração de medidas preventivas desse crescente problema de sáude pública. Espera-se que as hipóteses geradas neste estudo possam ser testadas em novas investigações que incorporem o desenho longitudinal, como o Estudo Pró-Saúde, no qual este se insere. / The study evaluates the association between job strain and self-reported medical diagnosis of repetitive strain injury (RSI). This is a cross-sectional study, included in the Pro-Saude Study, which consists of tracking a cohort of technical and administrative employees of a university in the State of Rio de Janeiro. The data were obtained in 2001 from the application of a self-administered questionnaire. The study population consisted of 3314 employees, among which 485 were self-reported medical diagnosis of RSI, after this admission to university. The prevalence of RSI was higther among women (19.4%) than amog men (8.8%). Job strain was assessed by the shortened version of Job Content Questionnaire, developed by Karasek and Theorell, whose questions are intended to assess the psychological demands, control over work, and social support. The analysis of job strain was performed according to the quadrants proposed by Karasek (1979): low strain (low demand and high control), passive job (low demand and low control), high strain (high demand and low control) and, active job (high demand and high control). In this analysis, was used as the reference category, the low strain, an ideal setting for composing work. After adjusting for socioeconomic and demographic variables (age, education and family income per capita) and occupational (years work and occupation), men and women with high demands at work were more likely to be affected by RSI (men : OR = 1.88, 95% CI 1.07; 3.29 and women: OR = 1.90, 95% CI 1.32; 2.02). In additional adjustment for social support at work, a reduction in strength of association for both sexes was founded. For women at high strain at work, this association remained significant (OR = 1.63, 95% CI 1.12 to 2.37), while for men, this association was marginally significant (OR = 1, 62, 95% CI 0.91 to 2.87). This study reinforces that the imbalance between job psycological demands and job control is important in the occurrence of RSI and therefore may be useful in developing preventive measures of this growing problem of public health. It is expected that the hypoteses generated in this study can be tested in further investigations that include the longitudinal design, as the Pro-Saude Study, in which it falls.

O presente estudo avalia a associação entre estresse no trabalho e auto-relato de diagnóstico médico de lesão por esforço repetitivo (LER). Trata-se de um estudo seccional, inserido no Estudo Pró-Saúde, que consiste no acompanhamento de uma coorte de funcionários técnico-administrativos de uma universidade no Estado do Rio de Janeiro. Os dados foram obtidos, no ano de 2001, a partir da aplicação de um questionário auto-preenchível. A população de estudo constou de 3.314 funcionários, dentre os quais, 485 apresentaram auto-relato de diagnóstico médico de LER, após sua admissão como funcionários da universidade. A prevalência de LER foi maior entre as mulheres (19,4%) do que entre os homens (8,8%). O estresse no trabalho foi avaliado através da versão reduzida do Job Content Questionnaire, desenvolvido por Karasek e Theorell, cujas questões se destinam a avaliar a demanda psicológica, o controle sobre o próprio trabalho e, o apoio social no trabalho. A análise do estresse no trabalho foi realizada de acordo com os quadrantes propostos por Karasek (1979): baixa exigência (baixa demanda e alto controle); trabalho passivo (baixa demanda e baixo controle); alta exigência (alta demanda e baixo controle) e; trabalho ativo (alta demanda e alto controle). Nesta análise, utilizou-se como categoria de referência, a baixa exigência, por compor um cenário ideal de trabalho. Após ajuste por variáveis socioeconômicas e demográficas (idade, escolaridade e renda familiar per capita) e, ocupacionais (anos de trabalho na universidade e ocupação), homens e mulheres com alta exigência no trabalho, apresentaram uma chance maior de serem acometidos por LER (homens: OR= 1,88; IC95% 1,07-3,29 e mulheres: OR= 1,90; IC95% 1,32-2,02). No ajuste adicional pelo apoio social no trabalho, houve redução da força da associação, para ambos os sexos. Para as mulheres com alta exigência no trabalho, esta associação manteve-se significativa (OR= 1,63; IC95%= 1,12-2,37); enquanto que para os homens, esta associação ficou marginalmente significante (OR= 1,62; IC95%= 0,91-2,87). Este estudo reforça que o desequilíbrio entre a demanda psicológica no trabalho e o controle sobre o próprio trabalho é importante na ocorrência de LER e, portanto, pode ser útil na elaboração de medidas preventivas desse crescente problema de sáude pública. Espera-se que as hipóteses geradas neste estudo possam ser testadas em novas investigações que incorporem o desenho longitudinal, como o Estudo Pró-Saúde, no qual este se insere. / The study evaluates the association between job strain and self-reported medical diagnosis of repetitive strain injury (RSI). This is a cross-sectional study, included in the Pro-Saude Study, which consists of tracking a cohort of technical and administrative employees of a university in the State of Rio de Janeiro. The data were obtained in 2001 from the application of a self-administered questionnaire. The study population consisted of 3314 employees, among which 485 were self-reported medical diagnosis of RSI, after this admission to university. The prevalence of RSI was higther among women (19.4%) than amog men (8.8%). Job strain was assessed by the shortened version of Job Content Questionnaire, developed by Karasek and Theorell, whose questions are intended to assess the psychological demands, control over work, and social support. The analysis of job strain was performed according to the quadrants proposed by Karasek (1979): low strain (low demand and high control), passive job (low demand and low control), high strain (high demand and low control) and, active job (high demand and high control). In this analysis, was used as the reference category, the low strain, an ideal setting for composing work. After adjusting for socioeconomic and demographic variables (age, education and family income per capita) and occupational (years work and occupation), men and women with high demands at work were more likely to be affected by RSI (men : OR = 1.88, 95% CI 1.07; 3.29 and women: OR = 1.90, 95% CI 1.32; 2.02). In additional adjustment for social support at work, a reduction in strength of association for both sexes was founded. For women at high strain at work, this association remained significant (OR = 1.63, 95% CI 1.12 to 2.37), while for men, this association was marginally significant (OR = 1, 62, 95% CI 0.91 to 2.87). This study reinforces that the imbalance between job psycological demands and job control is important in the occurrence of RSI and therefore may be useful in developing preventive measures of this growing problem of public health. It is expected that the hypoteses generated in this study can be tested in further investigations that include the longitudinal design, as the Pro-Saude Study, in which it falls.

The masters thesis is focused on design of the device for measurement of the aerodynamic forces and moments acting on radiators mounted in the wind tunnel test section. The thesis also includes the analysis of the aerodynamic drag which is produced by radiators and the LabView application software development.

Mg-Druckgusslegierungen sind aufgrund ihrer geringen Dichte potenzielle Leichtbauwerkstoffe. Ihre Festigkeitseigenschaften werden durch erhöhte Temperatur und die druckgussprozessbedingte Porosität maßgeblich beeinflusst. Zur Auslegung zyklisch belasteter Mg-Druckgussbauteile für eine begrenzte Betriebsdauer kann das Örtliche Konzept verwendet werden. Im Örtlichen Konzept nimmt das zyklische Werkstoffverhalten eine zentrale Rolle ein. Es umfasst das zyklische Verformungsverhalten und das zyklische Ermüdungsverhalten. Zur Beschreibung des zyklischen Werkstoffverhaltens werden die zyklische Spannungs-Dehnungs-Kurve für das Verformungsverhalten und die Dehnungswöhlerlinie für das Ermüdungsverhalten verwendet. Ziel der vorliegenden Arbeit ist es, die Einflüsse Temperatur und Porosität auf das zyklische Werkstoffverhalten der Mg-Druckgusslegierungen AZ91 und AM50 quantitativ zu erfassen. Dazu wird ein objektives Regressionsverfahren ermittelt, mit dem die zyklische Spannungs-Dehnungs-Kurve und die Dehnungs-Wöhler-Linie gemeinsam unter Einhaltung der Kompatibilitätsbedingungen aus den Daten einer Versuchsreihe regressiert werden können. Desweiteren wird eine Methodik entwickelt, mit der Ansätze zur quantitativen Erfassung von Einflüssen auf das zyklische Werkstoffverhalten aus Versuchsdaten abgeleitet werden können. Diese Methodik wird zur Untersuchung der Einflüsse Temperatur und Porosität auf das zyklische Werkstoffverhalten der Mg-Druckgusslegierungen AZ91 und AM50 angewendet. Die Untersuchungsergebnisse und deren Validierungen werden in dieser Arbeit vorgestellt. / Die-cast magnesium alloys are potential light-weight materials due to their low density. Their mechanical properties are significantly affected by elevated temperatures and by porosity, which die castings are especially prone to. The local strain approach can be used for dimensioning cyclically loaded magnesium die castings for a limited service life. The central role of this approach is assigned to the cyclic material behaviour. The cyclic material behaviour includes the cyclic deformation behaviour and the cyclic fatigue behaviour. It is characterized by the stress-strain curve for the cyclic deformation behaviour and by the strain-life curve for the cyclic fatigue behaviour. In the present work the aim is to describe the influence of elevated temperatures and of porosity on the cyclic material behaviour quantitatively. Therefore, a method is developed, which allows an objective and combined regression of the stress-strain curve and the strain-life curve for one test series. Furthermore, a methodology is developed, for deriving a formulation from experimental data to describe an arbitrary influence on the cyclic material behaviour quantitatively. This methodology is used to study the influences of elevated temperature and of porosity on the cyclic material behaviour of the die-cast magnesium alloys AZ91 and AM50. The results of the investigations and their validation are presented in this treatise.